Lamp focusing sight



May 26, 1936. w. T. HARDING LAMP FOCUSING SIGHT Filed Aug. 2'7, 1934 may as, loss go stares Paras? orrics' aerator (Granted under the not oi March 3, loss, as amended April fill, lttil: till G. G, lh'll The invention described herein may he mann factored and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to a lamp focusing sight for use in locating or focusing a lamp filament in a projector.

' The object of the invention is to provide a positive method of locating center of incandescent lamp filament for focusing purposes by which it is possible to focus the filament center more accurately than heretofore.

To this end the invention consists of a fixed sight constructed as part of, or as an attachment to, the filament support of an incandescent lamp so that when viewed from the side the end of the sight, being perpendicular to the center of the filament, may be used to focus the lamp filament.

'Other objects and advantages-of the invention will be apparent from the following detailed description of a specific embodiment thereof, read in connection with the accompanying drawing, whereas:-

Figure 1 is a horizontal section of an alrdome landing field fioodlight unit embodying the invention.

Figure 2 is an elevation, with part of the lamp housing broken away to more clearly show the lamp installation and focusing.

Figure 3 is an enlarged detail vicwoi a selected lamp filament as modified to incorporate the in= vention therein.

liigure 4 is a section on line ll-d of Figure 3,

and

Figure 5 is a View illustrating an alternate form of the invention.

For convenience of disclosure, the invention is shown and dmcribed as embodied in a a-coil monoplane filament lamp to which it is especially applicable but not limited. Referring more particularly to Figures 3 and 5, it will be noted that the 4-coil filament i is attached at its ends 8 to the lead-in wires 5 and is supported between the lead-4n wires with its coils vertical by a filament support 1 consisting usually of a thin wire having its lower end hooked around the filament as shown at 9, Figure 5, and its upper end fixed to an insulator ll connected to and bridging the space between the upper ends of the lead-in wires.

The lamp focusing sight constituting the sub- Ject matter of the present invention may be constructed as an integral part or the filament support I, as shown inFiaure 4, or it may be reps rate therefrom, as in Figure 5. In the first in stance, the support l is prolonged as at it, beyond the filament lioolr d to extend rearwardly and downwardly of the filament to a point coinciding with the filament center, the end it of the prolongation or sight it being perpendicular to the center oi the filament so that when viewed from the side it may be used to focus the lamp filament. When applied to the lamp as an attachment, as in Figure 5, the fixed sight consists merely of a sight wire Ila fixed at its upper end to, and depending from, the insulator H directly back of the filament supporting wire I with its lower end iia perpendicular to the center of the filament as shown.

A lamp of the 4-coil monoplane filament type is frequently used as a light source in a. parabolic reflector fioodlight, for illuminating an alrdome landing field. When so used, the plane of the lamp filament is placed parallel to the directrix plane of the parabola. Such fioodlights usually have peep sights and crosses for focusing the lamp. An airdome landing field fioodlight unit is conventionally shown in Figures 1 and 2, and consists of a lamp housing ll equipped with a lens is and a reflector it between which is located the lamp 23: the latter being adjustable in the lamp socket 25 to position its illuminating center, or filament center, at a desired point or focus. The lamp housing is provided with suitable means, such as peep holes lL-fil and th -29, defining lines of sight iii intersecting within the casing and at the desired or focal point for the filament center. since commercial filament lamps have no means definitely marking the filament center, the lamp focusing operation is subject to errors in judging the center location, since the center location when viewed at an angle, usually along lines of sight shown at iii, cannot be readily awertained. With the fixed sight arrangement of the invention, however, the filament center is definitely and positively marked and makes it possible to locate the filament center more accurately at the local point.

It will be understood that while the invention has been specifically shown and described as applied to a 4-coil monoplanc filament lamp, it is equally applicable to other types of filament lamps.

Having thus described the invention, what is claimed as new is:-

1. A filament lamp having, in combination, a lamp filament: afilament support: and a sighting element pointing to and positively indicating the center oi the filament tor lamp focusing purposes.

' 2. A filament lamp having, in combination, a lamp filament: lead-in wires for same: an insulator between the lead-in wires and above the filament: and a fixed sight depending from the the insulator to a point in line with the center 01 the filament.

3. A filament lamp having, in combination, alamp filament: lead-in wires for the same: an

" lamp filament and a filament support having a sight forming portion positively indicating the center of the filament for lamp focusing p. 5. A ent lamp having, in combination, a

20 filament: lead-in wires tor the same: an insulating bridge between the lead-in wires and above the filament: a filament support fixed to and depending i'rom said insulating bridge and in supporting connection with the filament, said filament support being prolonged beyond its connection with the filament to a point in line with the center of the filament to provide a fixed sight the end of which, when viewed from the side, is perpendicular to the filament center.

'6. A filament lamp having. in combination, a filament: lead-in wires for the same: an insulator between the lead-in wires and above the filament: a filament support depending from the insulator and engaging the filament: and a sight fixed to and depending from the insulator in a plane parallel to the plane of the filament and having its lower or sight end in line with the center of the filament.

WILBUR T. ING. 

